The invention relates to plugged dispenser cartridges for viscous dental materials. The invention provides improved plugged dental dispenser cartridges having at least one channel (passage or groove), which allows air to pass out of the chamber as it is filled with compressed viscous dental materials during plugging. This provides a plugged cartridge chamber filled with compressed viscous dental materials having low internal gauge pressure. The gauge pressure within the plugged cartridge chamber is lower than in prior art plugged cartridge chambers filled with viscous dental material. Beneficially, the invention provides less internal gauge pressure within the plugged cartridge chamber. A cap fits onto a needle cannula in fluid flow communication with the plugged cartridge chamber. Prior art plugged cartridges spontaneously extrude viscous dental material through the needle cannula causing cap loss during storage and transport of the plugged cartridge. Because there is less internal gauge pressure within the plugged cartridge chamber of the invention, such spontaneous extrusion and cap loss are effectively avoided.
Petrich et al in WO 00/44300 disclose a cartridge which at most is half filed with a high viscosity dental composition. The cartridge has a stepped chamber (26, 28) and a piston with two cylindrical portions (36 and 40) on a shank (38) for high viscosity dental compositions, such as restoratives, adhesives, cements etching gels, and sealants as see page 1 lines 30-32 and pages 5 and 6. The stepped chamber cartridge with two cylindrical pistons of Petrich et al requires a shank and first chamber which are about as long as the second chamber. The present invention overcomes the problems of the prior art by providing a cartridge almost entirely filled with a high viscosity dental composition in a single chamber with a single diameter, and has a single piston with a single outer diameter (and no shank).
During filling of prior art plugged cartridges with viscous dental restorative materials there is significant compression of air and viscous dental restorative materials. The compressed air is incorporated into the viscous dental material during filling. During subsequent storage of prior art plugged cartridges there is spontaneous extrusion of viscous dental material. Thus, during placement of a displaceable piston, compression of air takes place followed by partial extrusion of material. The sealed cartridges have substantial gauge pressure. During storage and transport of the plugged cartridge this results in cartridges breaking, and spontaneously extrusion of viscous dental material through the needle cannula causing cap loss. These problems of the prior art are overcome by the present invention. In the present invention air passes out of the cartridge through grooves in the chamber wall during placement of a displaceable piston. Because there is less internal gauge pressure within the plugged cartridge chamber of the invention, cartridge breakage, spontaneous extrusion and cap loss are effectively avoided. The invention provides controlled application of flowable or gel-form materials or medicinal products. Force applied to the cartridge body during extrusion is reduced by reducing the amount of air entrapped in the cartridge. This reduces the cartridge body internal gauge pressure. So when force is applied to the plug to extrude the composition, the total force on the cartridge body is less than in prior cartridges.
A dental cartridge chamber is filled with a high viscosity dental composition and a piston is pressed into the chamber. The piston has a generally cylindrical piston wall, an inner face and an outer face. The cartridge has a generally cylindrical chamber wall having at least one groove. Dental material is conveyed into the cartridge chamber. The cylindrical chamber wall encloses the dental composition and air. The air passes through the groove while the piston is pressed into the chamber. Pressing the piston causes it to move into the chamber. The outer face of the piston presses the high viscosity dental composition, as the cylindrical piston wall is guided along the cylindrical chamber wall. The chamber wall has at least one groove adjacent to the opening for the plug. The groove channel is open to the cartridge chamber. The groove channel extends through the external wall. As the plug is pressed into the cartridge chamber air passes from a cartridge chamber through the groove in a chamber wall. Thus, the piston is pressed into the cartridge chamber while gas passes from the cartridge chamber through the groove channel prior to hermetically sealing dental material in the cartridge chamber. The cartridge also has a discharge nozzle, a needle cannula and a cap. The needle cannula allows direct, precise and hygienic placement of dental materials and provides a dentist with visibility of material during application to a tooth.